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Passat b3 radiator fan doesn’t turn off

VW Passat B3 repair

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Sensor switch on the electric fan in the radiator Volkswagen Passat B3 installed two types:

VAG 91 959 481 A (C). 95-84C/102-91C, 3 plug

VAG 91 959 481 95-84C, 2 plug

The electric radiator fan switch sensor is installed in the cooling radiator in the lower right corner when facing the car.

Fuses responsible for protection of el. circuits: 13. signal, radiator fan or if the car with air conditioning, 19. radiator fan, air conditioning.

Common failure of the sensor in the radiator fan switch is a banal no contact closure (does not turn on the fan at one of the speeds). This sensor should be replaced, changing the sensor in the radiator fan, quickly and easily at home and does not require special tools and skills.

  • on a cold engine, remove wiring from the sensor
  • unscrew old sensor
  • screw in new sensor
  • connect wiring to the new sensor

Start the car engine and bring the coolant temperature up to the sensor temperature. the electric fan should start.

Loss of coolant when replacing the sensor maximum 100 grams., the time it takes this procedure is 5-10 minutes.

If you have any questions or additions, please do not hesitate to write in Комментарии и мнения владельцев.

In order to help the owners of Volkswagen Passat B3 in different regions of the world, I corrected the installation of advertising on the site and now ads are more tied to the region where the reader is, that is you. Now you can safely go to the ads, to find out the for parts and accessories in your area.

The fan runs on a cold motor: causes, diagnosis, repair

To begin with, the above problem can clearly indicate both the malfunction of the liquid cooling system, and the fan itself. In any case, we are talking about a breakdown, which can not be ignored, because the risk of overheating the engine significantly increases.

For better understanding it is necessary to consider superficially the principle of operation of the fan on most modern cars. Blowing is turned on by a special sensor that is located at the bottom of the radiator. Also many cars use a separate control unit for the engine cooling fan. There are also models in which the ECU itself is responsible for the fan activation, but such a design is rarely used.

As can be seen, the fan should not work on a cold engine. So, in order to determine why the fan is turning on early, for injector cars with OBD II diagnostic connector, it is recommended to start with the computer diagnostics of the car. The thing is that the possibility to read out error codes from ECU allows determining a cause of malfunction more accurately.

Also note that in cases where the control unit detects errors in the cooling system, the fan may spin immediately after turning on the ignition, even when the engine is cold. This feature is found only on some models and is, in fact, a protection against overheating of the power unit, since the constantly working fan reduces the temperature.

After repair in this case you will also need to perform error resetting. To erase the error from the ECU, on some models, it is enough to remove the terminal from the battery for a couple of minutes, while on other models, the resetting is made with the diagnostic equipment.

Common cooling fan problems

Now let’s look at the frequent problems that are associated with the cooling system and the fan itself.

  • the engine speed sensor contacts are short-circuited in many cases. In this case, there is blowing-off right after the ignition is turned on.

In the process of diagnostics on the cold sensor there is measured the resistance on the outputs with a multimeter. A deviation from the norm will indicate the need to replace the element.

  • There is not enough coolant in the liquid system. In this case the fan actuation is due to the fact that a small amount of antifreeze or toluene heats up very quickly. In other words, the fan is functioning properly and starts naturally.

As a rule, the leaking or low level of coolant in the expansion tank is the main reason. Note that the antifreeze is a mixture of concentrate and water. The water gradually evaporates from the system and causes the level to drop. For this reason, it is recommended to periodically check and refill the fluid according to special marks.

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The fan in this case can close on the battery and work nonstop. In such a situation you need to check all contacts, wiring and other elements. Wires must be securely insulated and properly connected.

  • The fan sensor that is integrated into the thermostat housing is defective. Quite a lot of modern machines are designed with a thermostat which is combined with a fan control sensor.

Such a solution allows for flexible control of the engine cooling system. But if there is a problem with the temperature sensor in the thermostat housing the fan can start without turning off. The point is that the control unit begins to receive incorrect signals about how the thermostat works. As a result, the emergency mode is activated, the fan starts and runs continuously.

passat, radiator, turn

In such a situation you need to check the sensor with a multimeter. In normal conditions, when the engine is cold, its resistance is infinite, in other cases the index should make 100 500 ohm. Deviations from the norm will indicate that the sensor should be replaced with a new or known good.

  • Outside air temperature sensor fails. Such problem is encountered on some vehicles that are equipped with ambient air temperature sensors. If the temperature is above the allowable limit, then these sensors activate the fan.

This solution allows for more efficient cooling of the power unit, especially in cars that have a powerful forced combustion engine and several radiators. On such units, the fan can be switched on during the warm season, even when the engine is cold, to protect the engine from overheating.

The problem may require external cleaning of the air conditioner radiator and cooling system radiator. The matter is that these radiators are next to each other and between them there is a lot of dust, lint and dirt. Removing such a “coat” allows you to normalize the air conditioning system and motor cooling, get rid of frequent fan activations and increased noise during its operation.

  • Problems with wiring and electrical contacts. Regardless of how the fan control is implemented, contacts become a frequent cause of problems.

To avoid this, experienced drivers recommend cleaning the contacts before the onset of winter and summer as a preventive measure. It is also common practice to treat it with special lubricants and protective coatings.

Fan switch sensor on the “Volkswagen Passat B3″: malfunction and replacement

If the fan in Passat B8 or B4 is permanently spinning, it means that the engine is starting to overheat. The thermostat can be the culprit.

The fan switch sensor (FST) is an important element in the engine cooling system. If it stops reacting to the temperature of the coolant, the system will stop working properly and the engine will fail.


To identify the car and reliable selection of the fan sensor Volkswagen Passat B3, B4 3A5,35I Universal, you should carefully select the modification of the vehicle. For this purpose, use the specifying information containing: horsepower, measured in horsepower (example 103 hp.с.), engine displacement (example 1.6 liter), type (example gasoline) and model engine code, as a rule, this parameter is rarely used, but you can find it only in the certificate of registration, you can also pay attention to the axle drive (may be rear, front or full), well and the mandatory parameter release date, divides the model t / c on restyling, before restyling, first and last year of production.

These data serve to uniquely install parts in a particular period of production, as manufacturers are constantly upgrading cars from the assembly line.

Passat B3 cooling fan does not turn on

That’s where you’re deeply mistaken. From the battery goes to the mounting block on the paint 19-th fuse is in the hood on the thermorelay (on the radiator).the fan its really depends on the ignition

Auto: Messages : 4398 Registered : 01 Oct 2012, 18:30 Thanks : 0 times. Reputation: 0

I will not argue. I will find some free time and be sure to look at the scheme for B3, really interested in how it works.

Auto: Messages : 4398 Registered : 01 Oct 2012, 18:30 Thanked : 0 times. Reputation: 0

The fan runs when the ignition is off for a long time maybe 4-5min.

Now this is the situation I turned off the engine, the fan runs, the fan stopped, I turn the ignition on (but do not start) and it turns on for a few more minutes.

not running one speed radiator fan

And most importantly when I remove the wires from the sensor in the radiator the fan continues to run.

Auto: Messages : 4430 Registered : 01 Oct 2012, 18:27 Thanked : 0 times. Reputation: 0

better go to an electrician, it seems that here have messed up already ukrainian

Auto: Messages : 4437 Registered : 29 may 2012, 17:54 Thank you :1 time. Rep: 0

Looked at the schematic, the B3 does have a different fan implementation, here is the schematic

F18.thermal switch. V7 cooling system fan motor. J138 Fan control unit after ignition off. F87 thermal switch 70 Garad. C for the fan to work after the ignition is turned off. V2 fan motor. N23 resistance for the fan. E9 fan switch.

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According to the diagram it turns out that the problem is either in the thermal switch F18, or in the fan control unit after turning off the ignition J138, or maybe faulty thermal switch F87 for fan operation after turning off the ignition (I understand that it is the temperature sensor under the hood). The temperature at which the fan should turn off should not exceed 70. C, that is, after the ignition is turned off, the fan motor runs until the temperature in the under-hood drops to 70 ° C. С. If I wrote something wrong, correct me. Have to drive up to the electrician to have him protest it all. The car is not new and has probably seen more than one owner

Auto: Messages : 4437 Posted : May 29, 2012, 17:54 Thanked :1 time. Reputation: 0

Auto : Messages : 4430 Registered : 01 Oct 2012, 18:27 Thanked : 0 times. Reputation: 0

F87 and J138 are not on every car, that is the circuit in some particular modification. I definitely didn’t have either by the time the climate was installed

Auto: Messages : 4345 Registered : 01 Oct 2012, 18:32 Thanked : 0 times. Reputation : 0

J138 is there and installed in the fuse box, so when the fan comes on this box clicks (relay)

Auto: Messages : 4437 Posted : May 29, 2012, 17:54 Thanked :1 time. Reputation: 0

I don’t have one. Now there is a clutch control unit for the condenser fans. On ABF motor there is an electric water pump, which works after the motor suppresses in order not to let the 16V head overheat

Auto: Messages : 4448 Registered : 15 Apr 2012, 23:32 Location : Moscow Thanks :1 time. Reputation: 1

Where do you start the search

If the fan does not turn off for a long time after stopping, you should start searching. You can’t replace the fusible link here, because it is not the culprit. Try to disconnect the connector from the sensor that is located on the bottom of the radiator. If it has stopped, it is faulty and must be replaced. You can drive your car without it for some time, but you should carefully monitor the temperature of the cooling fluid.

When checking it is desirable to have a meter such as a car tester or multimeter. Another culprit for this malfunction could be the temperature sensor in the thermostat housing. Specialists recommend to disconnect the connector and wires from it. Then unscrew the two nuts on its cover. After you turn on the ignition, everything should work in normal mode.

Комментарии и мнения владельцев 17

there is a sensor that when the car is heated to 100 degrees, gives weight regardless of the ignition, ie shut off the car and if the temp 100 then the sensor gives weight and while the car cools to something out there, it will not remove the mass feederobviously located near the valve cover

You don’t have to buy a topran, dello, etc.п. And buy hella, Knecht. Etc.д. Then there will be no problem, yes, it is more expensive by 2-3 timesbut buy and forget

Start with the simplest thing, unplug the connector from the temperature sensor on the radiator, if the car stops spinning it is probably the sensor is jammed.

Check the wire to the beech and to karson, BUV (block of fan control, located near the battery, disassemble and look at the board for breaks podapoly tracks), and the thermal switch on the fan motor (only removing it, near the slot there is a protective plate on three rivets, remove and immediately visible, there are two plates, one 1-2 speed-thin and direct transmission maximum-hard, if one of them melted, but rather will, then change the carlsone in assembly).The fan to check the work is very simple, close the terminals that go to the sensor on the radiator.

There’s no A/C unit, there’s no A/C or air conditioning, so there’s no A/C unit!

Comrade Vento 1.8 mono reel, bov there is.

It’s only available in versions with air conditioning or climate control! Either he’s got a kulibin rebuild!

I don’t know, I’ll check.)I had a vento without air conditioning but with a thermotronic and there was a.

The thermotronic has an air-conditioning compressor! Which means he’s got a boo-boo

what air conditioner compressor?)))) the thermotronic has a cabin temperature sensor and a smart heater with degrees on the torsion panel.)))

passat, radiator, turn

It’s only available in air-conditioning or air-cycle versions! He’s either got a kulibin modification!

Was not just for the air conditioner, or rather it has several tasks, to control the fans (speed) and afterburner.DIYers usually remove “superfluous” parts.

Why is the Ventilator VAZ 2114 constantly Runs

Sometimes motorists are faced with the fact that the cooling fan on VAZ 2114 constantly works. The causes of this phenomenon can be very different, and in order to fix it you must clearly understand what caused it. About why the fan stops turning off and how to fix it. we will talk in today’s article.

Cooling fan of VAZ 2114

Temperature sensor fuse

If the engine “boiled”, you should find the cause as soon as possible, so the situation will not repeat itself. Sometimes it’s because of the lack of coolant or clogged radiator, and sometimes the reason is that the radiator fan does not turn off. Do you know why it happens??

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The working temperature of the engine of the VAZ 2114 is about 87-89 degrees. Thermostat opens at 85 degrees and the cooler fan at standard firmware should turn on at 105 degrees and turn off at 97C.

Flushing the cooling system

If the coolant in the expansion tank has a muddy red color, it means there is contamination, which entails a malfunction. Clogged from time the radiator cooling system “Volkswagen Passat” B4 or B3 should be washed with a special liquid. Usually such products are colored in bright color. This measure is necessary to see if the cleaner is completely flushed out at the end of the work.

Flushing the cooling system. Source

Before starting the work it is necessary to drain about 30% of the old antifreeze and add the flushing agent. After that you need to add water up to the right level. Then start the car and gradually add fluid as the air lock will be gone. When the car reaches the working temperature it should work for 15-20 minutes. After it is necessary to drain the old antifreeze and flush all parts of the system. If the color of the water is clear, you can pour fresh coolant.

Operating principle of a radiator fan and causes of malfunctions (works all the time, does not work)

Before we consider this question, let’s touch on what a water-cooled ICE system is, shown in the figure below. It allows us to remember the principle of its operation.

When cold fluid passes through the motor jacket, it draws in excess heat, which cools the motor and heats the water. It then travels through the radiator where it gives off the heat it receives to the atmosphere and then back to the motor.

The design of the radiator is a set of thin tubes that create a large cooling surface. The oncoming flow of air as it passes through it takes away the excess heat that is stored in the fluid. When the air flow is not available (engine idling, traffic jams and other similar situations) or it is not sufficient to cool the water to the required temperature, the radiator fan.

There is a special control circuit for this, the basis of which is the radiator fan thermal switch. It controls the temperature of the liquid. When it exceeds the limits, the sensor is triggered, the signal turns on a radiator fan, which creates the necessary airflow. This flow cools the heated water and when the temperature reaches the required value, once again triggered the sensor and turns off the air circulation.

That’s how you can describe the basic principle by which the radiator fan operates. it turns on when the water temperature exceeds the desired value and turns off after reducing it to the desired value.

The heater did not work in 1, 2, 3 positions. SOLVED

And so one fine frosty morning I started the car to warm up, turned on the fan to 1 and left. I came about 10 minutes later, turned the fan to position 2, but the fan does not work, I switched to 3 and the same thing, and only on the 4 fan worked. After asking for help from the drivers and searching the forums it was 99% clear that the cause of the resistance of the heater.To get to it you need:Take off glove box (for which you need to unscrew 3 screws from the top, two from the bottom and two under the rails)There is such a picture:

Take off the chip and unscrew the screw (5 screwdriver)

Get the resistance. This is the culprit of the “triumph”:

Since it was not working 3 positions, and 3 resistors can hardly burn out, I checked the fuse with a tester, which was dead.

Then there are 4 options: 1. Order a new resistor (the most expensive option)2. At disassembly buy used (cheaper option) 3. Give it for repair (even cheaper option)4. Buy a new fuse in the components and solder itself.

I chose the 4th option because it is the fastest and cheapest.In radio components was bought thermal fuse at 240 degrees (as it was before) for 0.6 bucks.Next, everything is simple: remove the old and solder a new thermal fuse. Only you need to solder with high-temperature solder and be sure to heat sink, t.к. Thermal fuse can burnThe result:

Then we assemble in the reverse order and enjoy the working heater.Thanks to Serj2010, elve, wapriver for the tips. Special thanks to Passatuk.



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